One of the many acts that soured relations between the British and the Spanish during the Peninsula War was the destruction of the Roman Bridge at Alcantara. The bridge was built in 105 A.D. and is known as the Trajan Bridge after the Roman Emperor who reigned then. According to the editor of the Dickson Manuscripts "The bridge is made wholly of granite without the use of mortar. Its length is 616 feet; its width 26 feet. The two middle piers are about 190 feet high, and the two middle arches have a span of 150 feet. The usual depth of the water is 37 feet, but in time of flood it sometimes rises in the narrow gorge to a height of 180 feet." (Note: These dimensions are about: 190 meters long, 60 meters high, and 8 meters wide.) At the south end of the bridge is a small temple to a Roman god.
The bridge was of great military significance during the Peninsular War, for it is one of the few bridges across the Tagus River and the only one in western Spain. The Tagus River is wide at this point and goes through a series of canyons that makes access and fording very difficult.
Destruction of the bridge would make the Tagus a great obstacle and would add weeks on to any march north or south, due to the need to find another crossing place.
In May 1809, the French armies were victorious almost everywhere in the Iberian Peninsula. Although the British had retaken Portugal, they were considered too weak to challenge the French in Spain. In mid-May, Wellington sent a small force into western Spain to cut the French lines-of-communication that ran across the bridge at Alcantara. This force of about 2000 men was under the command of Colonel Mayne, a British officer. It consisted of:
1st Battalion, Loyal Lusitanian Legion
Idanha Nova Militia Regiment
6 lb Battery of the Loyal Lusitanian Legion (4 6-pounders, 2 howitzers)
1 squadron of the 11th Portuguese Cavalry (50 men)
When Marshal Victor heard of the Portuguese presence at Alcantara, he immediately marched to secure his lines-of-communication. This force of about 9,000 men, consisted of:
2nd Division (Lapisse)
16th Leger Regiment (3 Battalions)
8th, 45th, and 54th Line Regiments (3 Battalions each)
Dragoon Brigade (Identity Unknown)
Artillery (Size and numbers unknown)
By the 14th of May, the French had arrived in force in the vicinity of Alcantara. Colonel Mayne had the majority of his force in trenches on the north bank of the bridge, and had a small picquet of 50 infantry and his cavalry in the town on the south bank of the river, under the command of Lieutenant Colonel Grant. He also placed explosives to destroy the bridge in the event he was forced from his position. The following description of the fight was written by Colonel Mayne the night after the battle and can be found in his book The Campaigns of the Loyal Lusitanian Legion.
"At eight o'clock this morning Lieutenant-Colonel Grant perceiving three columns of the enemy approaching in three different directions, with artillery and cavalry, on the road from Brozas, behaved with his usual circumspection and having ascertained their strength, 10,000 infantry, 1500 cavalry, and 12 pieces of artillery, some of them 8 and other 12-pounders, very deliberately fell back on the position I had taken, destroyed the passes on either side of the bridge, which had been formed so as to be moved when the cavalry had passed over. Our artillery fired with great effect on the enemy entering the town, covering at the same time Lieutenant-Colonel Grant as he passed with his detachment over the bridge to join me. Our batteries composed of 6 guns of the Legion, were formed with fascines, gabions, &c. and calculated to defend the bridge; the infantry were formed on the heights, under the cover of some temporary breast works. About nine o'clock a very tremendous fire commenced from the two sides of the Tagus, which continued incessant; about 12 o'clock the militia regiment of Idania Nova, not being accustomed to any thing of this kind, and witnessing their officers and men falling and wounded on every side, made a precipitate retreat in a body leaving me occupying the heights of Alcantara, with the remnant of the Loyal Lusitanian Legion, (500 men) and the batteries of artillery. The French at one o'clock had seven guns all posted, bearing upon our position, and I thought it advisable to put fire to the mine of the bridge of Alcantara.
"...it only blew up on one side, leaving a free passage for the enemy across the Tagus. Thus situated, 1200 men of the Idania Regiment having basely left me, I had only one resort, which was, to give Lieutenant-Colonel Grant the command of the main battery, as the only means of preventing the enemy immediately pressing upon me while I effected a retreat. The cavalry of Almeida being reduced by fatigue from 50 to 20, were no cover to me, I therefore thought it advisable to sacrifice one field-piece for the security of the three others and the two howitzers; and finding Lieutenant Colonel Grant very ready to undertake the fighting of the main battery with this one piece. I moved away with the other five, and he did this from two 'clock to three... our ammunition being nearly wasted, and our killed and wounded surrounded us, it was absolutely necessary to adopt this mode of retreat with the few brave Lusitanians that were left; and to secure my artillery, the remaining gun was spiked and rendered of no use to the enemy on Lieutenant-Colonel Grant's leaving it to its fate..."
Although Mayne fired the explosives, it did not destroy the bridge. Enough of it remained for Victor sent a brigade of infantry across to secure the bridge and the Portuguese began to withdraw. Marshal Victor chose not to follow the retreating Portuguese and the battle ended. Casualties among the Loyal Lusitanian Legion were quite heavy, with over 250 men killed or wounded. Almost all from the heavy French artillery fire. Colonel Mayne stated that the Idanha Nova Militia Regiment deserted en masse.French casualties are difficult to determine, however, they were probably minimal, since there is no record of any officer casualties listed in Martinien's Tableaux par Corps et par Batailles des Officiers Tues et Blesses pendant les Guerres de L'Empire (1805-1815).
One of the mysteries about the bridge at Alcantara was when did the arch of the bridge finally collapse. No contemporary writer mentions when it fell, but within a year it had fallen completely. In addition to this, there is major confusion on what arch of the bridge was destroyed. A model of the bridge in the Spanish Army Museum shows it to be the third arch from the north bank. In the Dickson Manuscripts, there is a sketch done by him showing it to be the arch nearest the north bank. He also notes in his diary that "There were six arches, 5 of which are perfect, and the 6th, being the one on the opposite extremity from Alcantara, was broke down last year..." However, compounding this confusion is a sketch in the Royal Engineers Journal attributed to Major Sturgeon who built a temporary bridge at Alcantara. This sketch clearly shows it to be the second arch from the north bank. Based on Alexander Leith Hay's description below, it was most likely the second arch from the north bank.
The Spanish reaction to the destruction of the bridge was extremely negative, especially from those who were affected the most -- the people who lived in the area. Alexander Dickson noted in 1810 (a year after the bridge was destroyed) that "The Spaniards are very angry at its having been broke, and more so, as it has since been ascertained that it was done in consequence of the approach of a small body of cavalry only. They say that the bridge was permitted by the Goths, Moors, and other barbarous nations to exist without injury, but that at last it was destroyed by the Portuguese who are the most barbarous of all."
On 25 April 1812, Wellington ordered Major Sturgeon to repair the damage done to the bridge. About the same time, he ordered General Hill to destroy the French pontoon bridge at Almaraz - the only other bridge across the Tagus. By repairing the bridge at Alcantara Wellington was shortening the distance between the two main staging areas for his troops (Ciudad Rodrigo and Badajoz) to about 250 kilometers. By destroying the French pontoon bridge at Almaraz he would force the French to use the bridge at Toledo and effectively add another 650 kilometers to their march.
The best description of how the temporary bridge was constructed comes from Andrew Leith Hay, a British officer serving on the staff of his uncle, General Leith, the commander of the 5th Division.
"The arch destroyed was of so extensive a span, and the parapet of the bridge so great a height from the bed of the river, that no repair by using timber was practicable; the gap to be passed over being ninety feet wide, and the height of the bridge, one hundred and eighty from the bed of the river... The work was commenced by placing two beams on supporters four feet high and ninety feet asunder. These were secured to the side and end walls of the building by braces and tackles, to prevent their approximating by the straining of the ropes. Eighteen cables were then stretched round them, extending from end to end; eight pieces of timber, six inches square, at equal distances, were placed upon the ropes, with notches, one foot asunder, cut on their surface to secure them; these notches were seared with hot irons to prevent the ropes from chafing. The cables were then lashed to the beams; they were netted together by rope-yarn, and chains of sleepers were bolted and laid on the network, and secured to the two beams originally placed at the extremities of the work. Planks were cut and prepared for being laid across, bored at the ends so as receive a line destined to secure them to the sleepers and to each other... The next point was to prepare the edge of the fractured part of the bridge, and to cut channels in the masonry for the reception of the purchases. When arrived on the spot, four strong ropes were stretched from side to side, as conductors, for passing the cable-bridge across, the beam on the south side having been previously sunk into the masonry; the whole was then stretched by windlass erected on the opposite pier, by which means it was so tightly drawn as to prevent any great sinking, or the vibration which might render it insecure and dangerous, even when heavy weights were passed over."
A model of this bridge can be viewed at the Spanish Army Museum in Madrid.
The bridge was repaired in 1860 and there is no noticeable damage from the explosion. It is still in use and cars are permitted to drive across it. The best view of the bridge is from upstream since there is a hydroelectric dam about a kilometer east of the bridge, which ruins the view from downstream. A small car park and viewing area overlooking the bridge is on the south bank next to the Roman Temple.